A. Field
The present invention concerns an exchangeable choke for a fire arm with a smooth gun barrel.
B. Related Art
In particular, the invention concerns fire arms designed for shotgun cartridges whose charge, as is well known, consists of a certain quantity of small bullets or small balls of lead or another material.
It is known that when firing a cartridge, the impact of the lead shot has a certain dispersion which increases in proportion to the distance at which the impact takes place.
Said dispersion may be influenced by the use of what is called a choke.
The aim of this type of choke is to obtain a greater or lesser dispersion of the lead shot, whereby the choke forms a passage for the lead shot which extends in the continuation of the gun barrel and whose inner diameter is reduced in the direction of the muzzle of the gun barrel.
The course of the narrowing passage determines the degree of concentration of the impact of the lead shot.
The narrower the passage becomes, the higher the concentration of the impact.
The difference between the inner diameter of the gun barrel and the inner diameter at the muzzle is indicated by the term ‘chokage’.
Depending on the type of target and the distance up to the target, a larger or smaller chokage will be indicated or desirable.
Traditionally, the chokes for fire arms are divided in two categories, i.e. what are called ‘fixed chokes’ and ‘exchangeable chokes’.
In the case of fixed chokes, the chokage is realized in the mass of the gun barrel; to that end, the diameter of the gun barrel at the muzzle is varied as a function of the desired chokage.
Said fixed chokes are advantageous in that they do not require any additional maintenance.
They are disadvantageous, however, in that the chokage cannot be changed in a reversible manner depending on the shooter's needs.
Further, we know the category of exchangeable chokes.
An exchangeable choke comprises a bushing made of heat treated steel fixed to the inside of the muzzle of the gun barrel.
Here as well, the principle of the chokage is based on a reduction of the inner diameter in the direction of the muzzle of the gun barrel.
The advantage related to this category resides in that the chokage can be easily adapted to the needs of the shooter by mounting a choke having another configuration for the outlet diameter or by using a choke with variable chokage.
One of the inconveniences of these exchangeable chokes is that they tend to unscrew while shooting.
Another disadvantage of these exchangeable chokes is that they may get locked in the gun barrel.
Indeed, between the outer diameter of the choke and its seating or housing in the gun barrel, a functional clearance is indispensable.
Nevertheless, as a result, residues of powder, wad, lead shot, etc. may penetrate in the space between the choke and the gun barrel, such that, after a while, the piled dirt may cause the choke to get locked in the gun barrel of the fire arm. In that case, one may have to call a gunsmith to disassemble the parts or it may become entirely impossible to separate the latter without damaging them.
The problem is felt particularly in embodiments of chokes having an external screw thread by means of which the choke can be screwed in the housing of the gun barrel, whereby this housing is provided with a corresponding screw thread to that end. As fine screw threads are usually preferred, this mechanism is a delicate point of the screwed choke.
The present invention aims to provide a solution to one or several of the above-mentioned and other disadvantages.